SC1532

400mA SmartLDO MOSFET January 3, 2000 TM with Internal Pass SC1532 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION Intended for applications such as Power Managed PCI, the SC1532 is designed to maintain a glitch-free 3.3V output when at least one of two inputs, 5V (VIN1) and 3.3V (VIN2), is present. The SC1532 combines a 5V to 3.3V linear regulator with an integral 3.3V bypass switch, along with logic and detection circuitry to control which supply provides the power for the output. Whenever VIN1 exceeds a predetermined threshold value, the internal 3.3V PMOS linear regulator is enabled, and the internal pass NMOS is turned off. When VIN1 falls below a lower threshold value, the NMOS pass device is turned on and the PMOS linear regulator is turned off. This ensures an uninterrupted 3.3V output even if VIN1 falls out of specification. When both supplies are simultaneously available, the PMOS linear regulator will be turned on, and the NMOS pass will be turned off, thus preferentially supplying the output from the 5V supply. The internal 5V detector has its upper threshold (for VIN1 rising) set to 4.18V (typical) while the lower threshold (for VIN falling) is at 4.1V (typical) giving a hysteresis of approximately 80mV. The SC1532 is available in the popular SO-8 surface mount package. FEATURES Glitch-free transition between input sources Internal logic selects input source 5V detector with hysteresis 1% regulated output voltage accuracy ...